Compound for the aluminum film from chemical vapor depositions and the method of synthesis

ABSTRACT

Organometallic precursor compounds useful for forming aluminum films by chemical vapor deposition are disclosed. Also disclosed are methods of preparing the organometallic precursor compounds and methods of forming aluminum films.

BACKGROUND OF THE INVENTION

This invention generally relates to compounds used for the chemicalvapor deposition of metal films. In particular, this invention relatesto precursor compounds for use in the chemical vapor deposition ofaluminum films.

In the semiconductor industry, technological and material developmenthave resulted in the miniaturization, high reliability, high speed, highfunctionality, and high degree of integration of devices, such assemiconductor integrated circuits. With the development of themanufacturing process of semiconductor devices, the development ofimproved memory devices, such as dynamic random access memory ("DRAM"),has been rapid. Currently, 64 mega DRAM is under mass production and, inthe year 2,000, it is anticipated that with the new manufacturingmethods of the next generation semiconductor devices, as well as withtheir mass production capabilities, 256 mega class memory devices may beavailable, as well as 1 giga ("G") and 4 G class high memory devices.

The next generation memory devices, those having high memory capacity,are the result of miniaturization of the memory device circuits;specifically, narrowing the line widths to 0.25, 0.18, and 0.15 microns("μm").

The current wiring method in the semiconductor memory devices usingaluminum as the wiring material is by vapor deposition, i.e., thesputtering method in which a metal, i.e. aluminum, itself is used fordeposition to attain a desired thin film. This method limits themanufacturing process technology in achieving the narrowing of the linewidth described above.

In the manufacturing of 64 mega DRAM using aluminum (Al) metal wiring,the sputtering method has been the sole method used in the deposition ofaluminum from an aluminum target. In the next generation memory devicesdescribed above, the circuit line width would be less than 0.25 μm andthe aspect ratio (depth/diameter) of contact and via hole is large inthe vapor deposited metal, thus, the use of sputtering in the vapordeposition process would be unsuitable.

To alleviate such a problem, an aluminum wiring process using chemicalvapor deposition ("CVD") method has been studied for a long time. Thismethod has a high step coverage and has an improved burying process ofcontact/via hole, which is an advantage of the method. Thus, aluminumwiring from vapor deposition of aluminum ("Al-CVD" or aluminum chemicalvapor deposition) will be the foundation of the technology for theproduction of the next generation class memory devices and the CVDmethod is considered to be the imperative method.

In aluminum film deposition using the chemical vapor deposition method,an aluminum compound, known as the precursor, was used as the sourcematerial. The chemical properties and the selection of the compoundgreatly affect the CVD process and they are the most important elementsin the process. Therefore, prior to the selection of the depositionmethod, it is imperative that the selection and development of theprecursor are the first factors to be considered.

In spite of the importance of the role of a precursor, the metal filmdeposition process using CVD method has developed concurrently with theuse of the process in the manufacture of the next generationsemiconductor devices. For this reason the development of the precursorsfor Al-CVD has been delayed.

In the early stage of Al-CVD method development, alkyl aluminumcompounds were widely used in the industry. The typical alkyl aluminumcompounds commonly used were trimethylaluminum, as represented by thechemical formula of Al(CH₃)₃, and triisobutylaluminum, as represented bythe chemical formula of [(CH₃)₃ CHCH₂ ]₃ Al.

In the nineteen-nineties, the development of precursors for aluminumfilm deposition using the chemical vapor deposition process was veryactive in Japan resulting in the development of dimethylaluminumhydride, represented by the chemical formula of [(CH₃)₂ AlH]₂, and inthe U.S.A. resulting in the development of dimethylethylaminealane,represented by the chemical formula of H₃ Al:N(CH₃)₂ C₂ H₃. Thesecompounds were leading precursors in the Al-CVD process.

Among the chemical compounds examined, dimethylethylaminealane wassynthesized by Wayne Gladfelter of the University of Minnesota, in 1989,after the report of J. K. Ruff et al. in the Journal of the AmericanChemical Society, 1960. The synthesis of dimethylethylamine, (N(CH₃)₂ C₂H₃) has not been reported in the complex compound developed fromaluminum hydride (AlH₃) and an alkyl amine in the report. U.S. Pat. No.5,191,099 (Gladfelter et al.) discloses dimethylethylaminealane as aprecursor in Al-CVD process.

Other chemicals, such as dimethylaluminum hydride, trimethylaluminum,and triisobutylaluminum, have been developed and have been used widelyin various applications since the nineteen-fifties. Specifically,dimethylaluminum hydride was reported by T. Wartik et al., Journal ofAmerican Chemical Society, 1953, 75, 835, and trimethylaluminum andtriisobutylaluminum have been reported quite a bit earlier than theabove.

These compounds have been fully commercialized and used in manyindustrial areas prior to the nineteen-nineties. They can be obtainedeconomically, and they are liquid at room temperature, which are theiradvantages. However, the above-mentioned compounds have some problemswhen used as the precursors in the Al-CVD process. The film depositiontemperature is above 300° C. and near 400° C. Due to this highdeposition temperature, the vapor deposition process becomes verydifficult and the high temperature deposition results in the inclusionof carbon impurities which increase the electric resistance of thedeposited film, which are the detrimental flaws.

To alleviate such problems in the Al-CVD process, a dimethylaluminumhydride precursor and related technologies were developed in the earlypart of the nineteen-eighties. Dimethylaluminum hydride has a high vaporpressure (2 torr at 25° C.) and its vapor deposition rate is high and itis a colorless liquid compound at room temperature. Also,advantageously, it provides very pure aluminum film that can bedeposited at a low temperature (30° C.) when hydrogen gas is used as thereaction gas. However, dimethylaluminum hydride is an alkylaluminumcompound that explodes when it comes into contact with air. Therefore,it is very difficult to handle and has high degree of difficulty in themanufacturing process which results in a low yield and high cost.

As alternative precursors in the Al-CVD process, the alane (AlH₃)derivatives were used besides dimethylaluminum hydride. One of the alanederivatives, dimethylethylaminealane, forms a vapor deposition film ofhigh purity at low temperature, 100-200° C. Dimethylethylaminealane is acolorless chemical compound at room temperature and has a relativelyhigh vapor pressure (1.5 torr at 25 °C.). In comparison withdimethylaluminum hydride, the flammability is somewhat less and it canbe manufactured by a comparatively simple process at a low cost, whichis advantageous.

However, dimethylethylaminealane is thermally unstable at roomtemperature as well as during the vapor deposition process, which iscarried out at 30° to 40° C. Hence, during storage the precursorgradually decomposes in the container. This difficulty in roomtemperature storage is a disadvantage. For this reason, development andreproducibility of the vapor chemical deposition process has beendifficult in semiconductor device manufacturing processes.

SUMMARY OF THE INVENTION

It has now been found that certain aluminum compounds retain theadvantages of known precursors for aluminum film deposition and solvethe problems of these known precursors for Al-CVD applications.

The present invention provides an organometallic compound of the formula

    H(R').sub.2 Al:L.sub.n                                     (I)

wherein R' is an alkyl or perfluoroalkyl group having 1 to 4 carbons;and L is one or more Lewis bases capable of providing an unsharedelectron pair to the aluminum and is selected from thiophene, thiopyranor an organic amine of formula II or III ##STR1## wherein R is an alkylhaving a carbon number of 1 to 4; R¹, R², R²¹, R²², R²³ and R²⁴ are eachindependently hydrogen (H) or an alkyl group having carbon numbers of 1to 2; X is oxygen or an alkyl group containing nitrogen; m is an integerfrom 2 to 8; k and l are each independently integers from 1 to 3; and nis 1 or 2.

The present invention also provides a vapor deposition precursorcomposition comprising an organometallic compound described above.

The present invention also provides a process for aluminum filmformation comprising the step of vapor depositing an aluminum film on asubstrate, wherein the source of aluminum in the aluminum film is avapor deposition precursor comprising an organometallic compound of theformula H(R')₂ Al:L_(n) ; wherein R' is an alkyl or perfluoroalkyl grouphaving 1 to 4 carbons; and L is a Lewis base capable of providing anunshared electron pair to the aluminum and is selected from thiophene,thiopyran or an organic amine of formula II or III ##STR2## wherein R isan alkyl having a carbon number of 1 to 4; R¹, R², R²¹, R²², R²³ and R²⁴are each independently hydrogen (H) or an alkyl group having carbonnumbers of 1 to 2; X is oxygen or an alkyl group containing nitrogen; mis an integer from 2 to 8; k and l are each independently integers from1 to 3; and n is 1 or 2.

The present invention further provides a process for preparing anorganometallic compound of the formula H(R')₂ Al:L_(n) ; wherein R' isan alkyl or perfluoroalkyl group having 1 to 4 carbons; and L is one ormore Lewis bases capable of providing an unshared electron pair to thealuminum and is selected from thiophene, thiopyran or an organic amineof formula II or III ##STR3## wherein R is an alkyl having a carbonnumber from 1 to 4; R¹, R², R²¹, R²², R²³ and R²⁴ are each independentlyhydrogen (H) or an alkyl group having carbon numbers of 1 to 2; X isoxygen or an alkyl group containing nitrogen; m is an integer from 2 to8; k and l are each independently integers from 1 to 3; and n is 1 or 2,comprising the steps of: a) forming a suspension of trialkylaluminum ofthe formula R'₃ Al wherein R' is as defined above and lithium aluminumhydride in hexane or pentane; and b) adding to the suspension said Lewisbase.

DETAILED DESCRIPTION OF THE INVENTION

This invention pertains to organometallic compounds useful as precursorsin the vapor deposition of aluminum film as wiring on semiconductordevices and methods of preparing the precursor compounds. Specifically,the precursors are useful in the formation of an aluminum metal filmlayer on a diffusion barrier layer or adhesion layer on a siliconsubstrate.

Lewis bases capable of providing an unshared electron pair to thealuminum metal center are useful in the present invention. SuitableLewis bases include thiophene, thiopyran, and organic amine derivativesof Formula II or Formula III. For example, the organic amine derivativesinclude one or more heterocyclic amines selected from alkylaziridine,alkylazetidine, alkylpyrrolidine, alkylpiperidine,alkylhexamethyleneimine, alkylheptamethyleneimine, alkylmorpholine,1,4-dialkylpiperazine. ##STR4##

In the above Formula II, R is an alkyl having a carbon number of 1 to 4,R¹ and R² are each independently hydrogen (H) or an alkyl group havingcarbon numbers of 1 to 2, and m is an integer from 2 to 8. It ispreferred that R is methyl or ethyl. ##STR5##

In the above Formula III, R is an alkyl group having carbon numbers of 1to 4, R²¹, R²², R²³ and R²⁴ are each independently hydrogen (H) or alkylgroup having a carbon number of 1 to 2, X is oxygen or an alkyl groupcontaining nitrogen, and k and l are each independently integers of 1 to3.

Among the compounds expressed by Formula II, the preferred compounds arealkylaziridines having Formula IV, alkylpyrrolidines having Formula Vand alkylpiperidines having Formula VI. Among the compounds expressed byFormula III, the preferred compounds are alkylmorpholines having FormulaVII and alkylpiperazines having Formula VIII. ##STR6##

In the above Formula IV, it is preferred that R is methyl or ethyl andR² is hydrogen or methyl. It is more preferred that R and R² are bothmethyl. ##STR7##

In the above Formula V, R is an alkyl group having a carbon number of 1to 4, and R³ to R¹⁰ are each independently hydrogen or alkyl grouphaving a carbon number of 1 to 2. Preferred compounds of Formula V arethose wherein R³, R⁴, R⁶, R⁷, R⁹ and R¹⁰ are each independently hydrogenor methyl, more preferably wherein R⁵ and R⁸ are hydrogen, and mostpreferably wherein R is methyl, ethyl or butyl. 1-Methylpyrrolidine and1,4-dimethylpyrrolidine are particularly preferred. ##STR8##

In the above Formula VI, R is an alkyl group having a carbon number of 1to 4, and R¹¹ to R²⁰ are each independently hydrogen or an alkyl grouphaving a carbon number of 1 to 2. Preferred compounds of Formula VI arethose wherein R is methyl or ethyl, and R¹¹, R¹², R¹⁴, R¹⁶, R¹⁸, R¹⁹ andR²⁰ are each independently hydrogen or methyl. 1-Methylpiperldine,1-ethylpiperidine and 1,2,2,6,6-pentamethylpiperidine are particularlypreferred. ##STR9##

In the above Formula VII, R is an alkyl group having a carbon number of1 to 4, and R²⁵ to R³² are each independently hydrogen or an alkyl grouphaving a carbon number of 1 to 2. Preferred compounds of Formula VII arethose wherein R is methyl or ethyl and R²⁵, R²⁶, R²⁷, R²⁸, R²⁹, R³⁰, R³¹and R³² are each independently hydrogen or methyl. 4-Ethylmorpholine isparticularly preferred. ##STR10##

In the above Formula VIII, R is an alkyl group having a carbon number of1 to 4, and R³³ to R⁴⁰ are each independently hydrogen or an alkyl grouphaving a carbon number of 1 to 2. Preferred compounds of Formula VIIIare those wherein R is methyl or ethyl and R³³, R³⁴, R³⁵, R³⁶, R³⁷, R³⁸,R³⁹ and R⁴⁰ are each independently hydrogen or methyl. It is morepreferred that R is methyl and R³³, R³⁴, R³⁵, R³⁶, R³⁷, R³⁸, R³⁹ and R⁴⁰are each hydrogen.

Among the compounds defined by Formula II are those wherein the Lewisbase is an alkylpyrrolidine. The preferred alkylpyrrolidine is definedby Formula IX. The preferred compounds of Formula IX are those whereinR³, R⁴, R⁶, R⁷, R⁹ and R¹⁰ are each independently hydrogen or methyl.The compounds defined by Formula IX include: 1,2-dimethylpyrrolidinehaving Formula X, 1-methylpyrrolidine having Formula XI, and1-butylpyrrolidine having Formula XII. Among the compounds defined byFormula II are those wherein the Lewis base is an alkylpiperidine,having Formula VI, and preferably an alkylpiperidine having FormulaXIII. It is more preferred that the alkylpiperidine is1,2,2,6,6-pentamethylpiperidine having Formula XIV, 1-methylpiperidinehaving Formula XV, and 1-ethylpiperidine having Formula XVI. ##STR11##

Among the compound defined by Formula III are those wherein the Lewisbase is an alkylmorpholine shown by Formula VII. The preferred compoundsdefined by Formula VII include: 4-methylmorpholine having Formula XVIIand 4-ethylmorpholine having Formula XVIII. Additionally, amongalkylpiperazines having Formula VIII, the preferred one is1,4-dimethylpiperazine, shown by Formula XIX. ##STR12##

Thus, the preferred organic amines are 1,2-dimethylpyrrolidine,1-methylpyrrolidine, 1-butylpyrrolidine, 1,4-dimethylpyrrolidine,1-methylpiperidine, 1-ethylpiperidine, 1,2,2,6,6-pentamethylpiperidine,4-methylmorpholine, 4-ethylmorpholine and 1,4-dimethylpiperazine.

An aluminum compound represented by Formula I used for aluminum filmvapor deposition can be readily prepared according to the chemicalreaction represented by Equation 1. Hexane or pentane was added to amixture of trialkylaluminum (Al(R')₃), and lithium aluminum hydride(LiAlH₄) in a reactor at room temperature to form a suspension and thena Lewis base, L, such as alkylpyrrolidine, alkylpiperidine,alkylmorpholine and alkylpiperazine, was added to obtain the compoundsof the present invention.

    LiAlH.sub.4 +Al(R').sub.3 +nL→H(R').sub.2 Al:L.sub.n +LiAlH.sub.3 (R')                                                      Equation 1

In the above Equation 1, R' is an alkyl or perfluoroalkyl group withfrom 1 to 4 carbons, L is a Lewis base, and n is 1 or 2, as defined inFormula I. It is preferred that R' is methyl.

Among the Lewis base compounds useful in the present invention, thepreferred are 1-methylpyrrolidine and 1-ethylpiperidine. Thus, thetypical precursors for the vapor deposition of aluminum film as wiringmaterial in semiconductor device manufacture are the compoundsrepresented by Formula XX, which is 1-methylpyrrolidinedimethylaluminumhydride, and Formula XXI, which is 1-ethylpiperidinedimethylaluminumhydride. The invention will be discussed in relation to these twocompounds, namely the use of these compounds as precursors in aluminumfilm vapor deposition. ##STR13##

Dimethylaluminum hydride is well known as a precursor in aluminum filmvapor deposition, and has been in use since the nineteen-eighties.However, a problem with this compound is its high viscosity and solvingthis viscosity problem will provide control in attaining a properdelivery rate when a bubbler or other liquid delivery system is used asthe transporting system. The ease of the delivery rate control is veryimportant in semiconductor device manufacture. Also important is thereproducibility in the aluminum film vapor deposition process, and suchreproducibility allows for the development of aluminum vapor depositionprocess.

Conventional aluminum chemical vapor deposition ("CVD") precursorcompounds, such as dimethylethylaminealane, trimethylaluminum anddimethylaluminum hydride, etc., ignite explosively when they contactwater or air. The invention compounds are flammable but they do notignite explosively or they are less flammable than the conventionalprecursors, so the risks of fire and personal injury are reduced.

The process of manufacturing the compounds can be carried out with easeand without any danger, yet the yield is high when compared with themanufacturing process of dimethylaluminum hydride. Moreover, the unitproduction cost will be less than that of dimethylaluminum hydride.Thus, it is expected that the compounds of the present invention wouldbe excellent precursors in aluminum film vapor deposition by usingchemical vapor deposition process.

The invention compounds are a liquid at room temperature, and thus, thecontrol of the precursor compound delivery rate, which is closelyrelated to process reproducibility, is easily achieved in the vapordeposition process by using a bubbler. Also, in other chemical vapordeposition processes that use a direct liquid injector or a liquiddelivery system, the process can be easily carried out, which is anadvantage. In a chemical vapor deposition process, the compounds of thepresent invention may be vaporized by thermal energy, plasma or a biasapplied on the substrate.

Furthermore, as an added feature, the inventors developed precursorcompound solutions which are more beneficial than known precursorsolutions used in delivery systems such as direct liquid injectors andliquid delivery systems. A heterocyclic amine was used as the solventfor the preparation of a precursor solution for the delivery of theprecursor compounds of Formula I, the solute, in a delivery system.Examples of the heterocyclic amine solvent include 1-methylpyrrolidine,1-butylpyrrolidine, 1-methylpiperidine, 1-ethylpiperidine,4-methylmorpholine, 4-ethylmorpholine, 1,4-dimethylpiperazine, and thelike. It is preferred that the solvent is 1-methylpyrrolidine. Thesolutes and the solvents are used in various combinations, and theresulting aluminum compound solutions can be used as effectiveprecursors in aluminum vapor deposition processes.

In aluminum film vapor deposition, the invention solutions allow for thedevelopment of new processes when compared with that of conventionalprecursor solutions due to the wide selection of precursors.

Solutions of the above new compounds represented by Formula I wereprepared using a heterocyclic amine as the solvent. The new precursorcompound solution can be prepared by dissolving the invention compoundrepresented by Formula I in a heterocyclic amine which is free of water,a purified solvent, and a Lewis base. The entire reaction is carried outunder an inert gas atmosphere, such as a nitrogen or argon stream, toprevent the deterioration of the compound due to exposure to air.

The invention compounds and the preparation of solutions of the compoundwill be discussed with examples.

EXAMPLE 1 Synthesis of 1-Methylpyrrolidinedimethylaluminum hydride

To a stirred, powder suspension of 198 g (2 moles) of trimethylaluminumand 95 g (2 moles) of lithium aluminum hydride in pentane under nitrogenstream at room temperature were added dropwise 212 g (2.5 moles) ofcolorless 1-methylpyrrolidine. The heat of the reaction was minute andit was not necessary to cool the reactor. The heat may have aided thereaction. Following the addition of 1-methylpyrrolidine, the reactionwas allowed to stir for about 5 hours at room temperature.

After the completion of the reaction, the invention compound, which is1-methylpyrrolidinedimethylaluminum hydride, was separated from thereaction mixture by filtration under a nitrogen stream to obtain acolorless, first filtrate. The byproducts on the filter were rinsedtwice with a sufficient quantity of pentane, and then the rinsingsolutions were added to the first filtrate. All of the volatilecomponents in the filtrate were removed under vacuum at room temperatureto obtain a colorless liquid.

The dried colorless filtrate was distilled at 45° C. under vacuum (10⁻²torr) and the distillate was condensed in a receiver chilled with dryice. The colorless first distillate was processed in a similar manner at40° C. to purify and to obtain 250 g of high purity1-methylpyrrolidinedimethylaluminum hydride.

The reaction shown in Equation 2 is the preparation of1-methylpyrrolidinedimethylaluminum hydride, and the highly purified1-methylpyrrolidinedimethylaluminum hydride was analyzed by protonnuclear magnetic resonance (NMR), and the data and properties are listedin Table 1. ##STR14##

EXAMPLE 2 Synthesis of 1-Butylpyrrolidine

To a suspension of trimethylaluminum and lithium aluminum hydride inpentane prepared according to the procedure of Example 1, 279 g (2.2moles) of 1-butylpyrrolidine were added dropwise at room temperatureunder a nitrogen stream and the mixture was stirred for 5 hours whileheating. After filtration according to Example 1, the resulting filtratewas dried to obtain a colorless liquid.

The dried colorless liquid compound was distilled at 50° C. under vacuum(10⁻² torr), and collected in a receiver chilled with dry ice (-78° C.)to obtain colorless, high purity 1-butylpyrrolidinedimethylaluminumhydride (332 g).

The reaction shown in Equation 3 is the preparation of1-butylpyrrolidinedimethylaluminum hydride, and the compound wasanalyzed by proton nuclear magnetic resonance. The data and the observedproperties are listed in Table 1. The results confirmed the compound as1-butylpyrrolidinedimethylaluminum hydride. ##STR15##

EXAMPLE 3 Synthesis of 1-Methylpiperidinedimethylaluminum hydride

To a suspension of trimethylaluminum and lithium aluminum hydride inpentane according to the procedure of Example 1, 218 g (2.2 moles) of1-methylpiperidine were added dropwise at room temperature under anitrogen stream, and the reaction mixture was stirred for 5 hours. Afterfiltration according to Example 1, the colorless filtrate was driedunder vacuum to obtain a colorless liquid.

The dried colorless liquid compound was distilled at 45° C. under vacuum(10⁻² torr) and the distillate was collected in receiver chilled withdry ice (-78° C.) to obtain 280 g of colorless, high purity1-methylpiperidinedimethylaluminum hydride.

The reaction shown in Equation 4 is the preparation of1-methylpiperidinedimethylaluminum hydride, and the product compound wasanalyzed by proton nuclear magnetic resonance. The data and the observedproperties are listed in Table 1 and the product was confirmed as1-methylpiperidinedimethylaluminum hydride. ##STR16##

EXAMPLE 4 Synthesis of 1-Ethylpiperidinedimethylaluminum hydride

To a suspension of trimethylaluminum and lithium aluminum hydride inhexane prepared according to the procedure of Example 1, 249 g (2.2moles) of 1-ethylpiperidine were added dropwise at room temperatureunder a nitrogen stream and the reaction was carried out according toExample 1. The product was filtered, dried, and distilled to obtain 308g of colorless high purity 1-ethylpiperidinedimethylaluminum hydride.

The reaction shown in Equation 5 is the preparation of1-ethylpiperidinedimethylaluminum hydride, and the product compound wasanalyzed by proton nuclear magnetic resonance. The data and the observedproperties are listed in Table 1, and the product was confirmed as1-ethylpiperidinedimethylaluminum hydride. ##STR17##

EXAMPLE 5 Synthesis of 4-Ethylmorpholinedimethylaluminum hydride

To a suspension of trimethylaluminum and lithium aluminum hydride inpentane prepared according to the procedure of Example 1, 253 g (2.2moles) of 4-ethylmorpholine were added dropwise at room temperatureunder a nitrogen stream and the reaction was carried out according toExample 1. After the completion of the reaction, the reaction productobtained by the procedure of Example 1 was separated to obtain 310 g of4-ethylmorpholinedimethylaluminum hydride.

The reaction shown in Equation 6 is the preparation of4-ethylmorpholinedimethylaluminum hydride, and the product compound wasanalyzed by proton nuclear magnetic resonance. The data and the observedproperties are listed in Table I and the product was confirmed as4-ethylmorpholinedimethylaluminum hydride. ##STR18##

EXAMPLE 6 Synthesis of 1,4-Dimethylpiperazinedimethylaluminum hydride

To a suspension of trimethylaluminum and lithium aluminum hydride inpentane prepared according to the procedure of Example 1, 250 g (2.2moles) of 1,4-dimethylpiperazine were added dropwise at room temperatureunder a nitrogen stream and the reaction was carried out according toExample 1. After the completion of the reaction, the reaction productobtained by the procedure of Example 1 was separated to obtain 260 g of1,4-dimethylpiperazinedimethylaluminum) hydride.

The reaction shown in Equation 7 is the preparation of1,4-dimethylpiperazinedimethylaluminum hydride, and the product compoundwas analyzed by proton nuclear magnetic resonance. The data and theobserved properties are listed in Table 1, and the product was confirmedas 1,4-dimethylpiperazinedimethylaluminum hydride. ##STR19##

                  TABLE 1                                                         ______________________________________                                        Ex-                  Phase          NMR Analysis                                ample Compound (20° C.) Color (C.sub.6 D.sub.6, ppm)                 ______________________________________                                        1     1-Methylpyrro- liquid  colorless                                                                            δ -0.55 (s, 3H)                        lidinedimethyl-   δ -0.50 (s, 3H)                                       aluminum hydride   δ -0.40 (s, 1H)                                         δ 1.30 (m, 4H)                                                          δ 1.85 (s, 3H)                                                          δ 2.40 (br, 4H)                                                         δ 4.10 (br)                                                         2 1-Butylpyrro- liquid colorless δ -0.45 (s, 3H)                         lidinedimethyl-   δ -0.38 (s, 3H)                                       aluminum hydride   δ -0.33 (s, 1H)                                         δ 0.78 (t, 3H)                                                          δ 1.00 (m, 2H)                                                          δ 1.38 (br, 6H)                                                         δ 2.28 (t, 2H)                                                          δ 2.45 (br, 4H)                                                         δ 4.10 (br)                                                         3 1-Methylpiperi- liquid colorless δ -0.60 (s, 3H)                       dinedimethyl-   δ -0.55 (s, 3H)                                         aluminum hydride   δ -0.45 (s)                                             δ 1.05 (br, 2H)                                                         δ 1.20 (br, 4H)                                                         δ 1.95 (s, 3H)                                                          δ 2.38 (br, 4H)                                                         δ 4.05 (br)                                                         4 4-Ethylpiperi- liquid colorless δ -0.42 (s, 6H)                        dinedimethyl-   δ 0.85 (t, 3H)                                          aluminum hydride   δ 1.05 (br, 2H)                                         δ 1.15 (br, 4H)                                                         δ 2.35 (q, 2H)                                                          δ 2.45 (br, 4H)                                                         δ 4.15 (s, 1H)                                                      5 4-Ethylmorpho- liquid colorless δ -0.48 (s, 6H)                        linedimethyl-   δ 0.75 (t, 3H)                                          aluminum hydride   δ 2.10 (m, 2H)                                          δ 2.13 (p, 4H)                                                          δ 3.58 (p, 4H)                                                          δ 4.17 (s, 1H)                                                      6 1,4-Dimethylpiper- solid colorless δ -0.55 (s, 3H)                     azinedimethyl-   δ -0.50 (s, 3H)                                        aluminum hydride   δ -0.45 (s)                                             δ 1.83 (s, 6H)                                                          δ 2.33 (s, 8H)                                                          δ 4.05 (br)                                                       ______________________________________                                    

EXAMPLE 7 Preparation of 1-Methylpiperidinedimethylaluminum hydride inSolution of 1-Methylpiperidine

To 80 g of the liquid compound, 1-methylpiperidinedimethylaluminumhydride, from Example 3, were added 20 g of purified 1-methylpiperidinewas added to yield a colorless solution.

EXAMPLE 8

Among the compounds of the invention,1-methylpyrrolidinedimethylaluminum hydride prepared according toExample 1,1-ethylpiperidinedimethylaluminum hydride prepared accordingto Example 4, and the 1-methylpiperidinedimethylaluminum hydridesolution prepared according to Example 7 were tested for aluminum filmvapor deposition by the is following procedure.

Test 1

The compounds synthesized in Example 1 and Example 4,1-methylpyrrolidinedimethylaluminum hydride and1-ethylpiperidinedimathylaluminum hydride, respectively, were each addedto a stainless steel bubbler, and then heated to 40° to 50° C. Argon ornitrogen gas was used as the carrier gas by bubbling through thesolution at a flow rate of 100-600 SCCM (standard cubic centimeters perminute or cm³ /minute).

The vaporized precursor compound was diluted by reducing hydrogen gasand passed through a stainless steel tube heated to 40° to 60° C. andinto a reactor containing a substrate for film vapor deposition.

The walls of the reactor were heated to 40° to 60° C. to preventcondensation of the precursor. The substrates used were 2,000 Angstromthick SiO₂ with a vapor deposited 900 Angstrom thick TiN (titaniumnitride) layer. The substrates were heated at 200° to 300° C. for thevapor deposition of a high purity aluminum film. The vapor depositedaluminum film was measured for the impurity content by Auger electronspectroscopy ("AES") and it was confirmed that the vapor depositedaluminum film was high purity. The sheet resistance was measured by a4-point probe. The vapor deposition conditions and the analytical dataare listed in Table 2.

                                      TABLE 2                                     __________________________________________________________________________                 1-Methylpyrrolidinedimethyl-                                                               1-Ethylpiperidinedimethyl-                            Precusor: aluminum hydride aluminum hydride                                 __________________________________________________________________________    Deposition Condition                                                            Carrier Gas Nitrogen Argon                                                    Reacting Gas Hydrogen Hydrogen                                                Bubbler Temperature (° C.) 40-50 40-50                                 Reactor Temperature (° C.) 40-60 40-60                                 Substrate Temperature (° C.) 200-300 200-300                           Flow rate (SCCM) 100-600 100-600                                              Reactor Pressure (torr) 0.1-6 0.1-6                                           Thin Film                                                                     Deposition Rate (Å/min) 1000-10,000 1000-10,000                           Resistivity (μohm-cm) 2.8-3.5 2.8-3.5                                      Impurity None (by AES) None (by AES)                                          Adhesion Excellent on Titanium nitride Excellent on Titanium nitride                                   Surface Reflectivity Good Good                     __________________________________________________________________________

Test 2

The precursor compound solution prepared according to the procedure ofExample 7 was used to form an aluminum film by chemical vapor depositionmethod. The silicon substrate was the same as the one used in Test 1 andthe substrate temperature was 200° to 300° C. The reactor vessel, aglass tube having 5 cm inside diameter and 30 cm length, had one closedend and the open end was connected to a vacuum pump (10⁻² torr). Theprecursor solution was filled in a 2 milliliter ("mL") glass containerand the glass container was placed in the closed end of the reactor.Several thin silicon pieces were placed in the reactor. The precursorsolution and the substrate were maintained at 45° C. and 200° to 300°C., respectively, using independent heating wires. While heating thesolution and the substrates, the reactor was evacuated by vacuum pump to10⁻² torr to obtain a vapor deposited high purity aluminum film. Thevapor deposited film was tested by Auger electron spectroscopy ("AES")and 4-point probe testing. The results, which confirmed that thealuminum film was high purity, are listed in Table 3. This further showsthat the invention solution is suitable for direct liquid injector andliquid delivery system as the liquid precursor delivery system.

                  TABLE 3                                                         ______________________________________                                                          1-Methylpiperidinedimethyl-                                    aluminum hydride                                                             Precursor: dissolved in 1-Methylpiperidine                                  ______________________________________                                        Deposition Condition                                                            Reacting Gas Hydrogen                                                         Evaporation Temperature (                                                                     ° C.) 45                                               Substrate Temperature (° C.) 200-300                                   Reactor Pressure (torr) 0.1-1                                                 Thin Film                                                                     Resistivity (μohm-cm) 2.5-3.2                                              Impurity None (by AES)                                                        Adhesion Excellent on Titanium nitride                                        Deposition Rate (Å/min) 1000-10,000                                     ______________________________________                                    

The compounds of the invention can be vapor deposited to form thin filmsat a wide range of substrate temperature, namely 200° to 300° C. Also,the deposition rate of aluminum film on a silicon substrate,resistivity, impurity level, adhesion strength, and reflectance aresuperior to those obtained using known precursors. Moreover, theprecursors of the invention can be used in direct liquid injector orliquid delivery system in the vapor deposition process, which is anadvantage.

What is claimed is:
 1. An organometallic compound of the formula

    H(R').sub.2 Al:L.sub.n                                     (I)

wherein R' is an alkyl or perfluoroalkyl group having 1 to 4 carbons;and L is one or more Lewis bases capable of providing an unsharedelectron pair to the aluminum and is selected from thiophene, thiopyranor an organic amine of formula II or III ##STR20## wherein R is an alkylhaving a carbon number of 1 to 4; R¹, R², R²¹, R²², R²³ and R²⁴ are eachindependently hydrogen or an alkyl group having carbon numbers of 1 to2; X is oxygen or an alkyl group containing nitrogen; m is an integerfrom 2 to 8; k and l are each independently integers from 1 to 3; and nis 1 or
 2. 2. The compound of claim 1, wherein the organic amine is oneor more selected from alkylaziridine, alkylazetidine, alkylpyrrolidine,alkylpiperidine, alkylhexamethyleneimine, alkylheptamethyleneimine,alkylmorpholine, or alkyipiperazine.
 3. The compound of claim 2, whereinthe organic amine is one or more selected from 1,2-dimethylpyrrolidine,1-methylpyrrolidine, 1-butylpyrrolidine, 1-methylpiperidine,1-ethylpiperidine, 1,2,2,6,6-pentamethylpiperidine, 4-methylmorpholine,4-ethylmorpholine or 1,4-dimethylpiperazine.
 4. A vapor depositionprecursor composition comprising an organometallic compound of claim 1and a heterocyclic amine solvent is.
 5. The composition of claim 4,wherein the heterocyclic amine solvent is one or more selected from1-methylpyrrolidine, 1-butylpyrrolidine, 1-methylpiperidine,1-ethylpiperidine, 4-methylmorpholine, 4-ethylmorpholine, or1,4-dimethylpiperazine.
 6. A process for preparing an organometalliccompound of the formula H(R')₂ Al:L_(n) ; wherein R' is an alkyl orperfluoroalkyl group having 1 to 4 carbons; and L is one or more Lewisbases capable of providing an unshared electron pair to the aluminum andis selected from thiophene, thiopyran or an organic amine of formula IIor III ##STR21## wherein R is an alkyl having a carbon number from 1 to4;R¹, R², R²¹, R²², R²³ and R²⁴ are each independently hydrogen or analkyl group having carbon numbers of 1 to 2; X is oxygen or an alkylgroup containing nitrogen; m is an integer from 2 to 8; k and l are eachindependently integers from 1 to 3; and n is 1 or 2,comprising the stepsof: a) forming a suspension of trialkylaluminum of the formula R'₃ Alwherein R' is as defined above and lithium aluminum hydride in hexane orpentane; and b) adding to the suspension said Lewis base.
 7. The processof claim 6, wherein the organic amine is one or more selected from1,2-dimethylpyrrolidine, 1-methylpyrrolidine, 1-butylpyrrolidine,1-methylpiperidine, 1-ethylpiperidine, 1,2,2,6,6-pentamethylpiperidine,4-methylmorpholine, 4-ethylmorpholine or 1,4-dimethylpiperazine.